Rod-pump controller

Abstract

A rod-pump control device is disclosed. The claimed rod-pump control device uses fuel or air usage for gas units, and can use pressure. The sensors work as the primary trigger to indicate a pump-off condition on an oil and gas well. These sensors can be used as stand-alone triggers or in conjunction with other sensors to more accurately monitor pump efficiency. When the pump-controller starts to indicate an inefficient pump condition, it will remove power to disengage an electric clutch or send a signal to an engine controller to stop. An adjustable algorithm will use percentage change of off time, dependent on actual run time compared to a user definable target time to keep the pump operating at peak efficiency.

Claims

1. A rod-pump control device comprising: (a) a power sensor configured to measure a power used by a rod pump, wherein the power sensor includes at least one of the group consisting of a fuel-consumption sensor configured to monitor fuel consumed by a gas-powered rod pump and an air-consumption sensor configured to monitor air consumed by a gas-power rod pump; and (b) a control circuit connected to the power sensor and configured to read a power measurement from the power sensor and to selectively disable the rod pump based on the power measurement.

2. The rod-pump control device of claim 1 wherein the control circuit comprises at least one of the group consisting of a processor, an application-specific circuit, and a programmable logic controller.

3. The rod-pump control device of claim 1 further comprising a tubing-pressure sensor and wherein the control circuit is connected to the tubing-pressure sensor and is further configured to read a tubing-pressure measurement from the tubing-pressure sensor and to selectively disable the rod pump based on the tubing-pressure measurement.

4. The rod-pump control device of claim 1 further comprising a polish-rod temperature sensor and wherein the control circuit is connected to the polish-rod temperature sensor and is further configured to read a polish-rod-temperature measurement from the polish-rod temperature sensor and to selectively disable the rod pump based on the polish-rod-temperature measurement.

5. The rod-pump control device of claim 1 wherein the control circuit is configured to selectively disable the rod pump when a time variance in the power measured by the power sensor exceeds a predetermined level of acceptable variance.

6. The rod-pump control device of claim 1 wherein the control circuit is configured to modify, using a rod-pump run time and a target run time, at least one of the group consisting of the rod-pump duty cycle, the rod-pump period, and the rod-pump off time.

7. A method for controlling operation of a gas-powered rod pump, the method comprising: (a) measuring a power used by the gas-powered rod pump using a power sensor that includes at least one of the group consisting of a fuel-consumption sensor configured to monitor fuel consumed by the gas-powered rod pump and an air-consumption sensor configured to monitor air consumed by the gas-power rod pump; and (b) disabling the rod pump based on the measured power.

8. The method of claim 7 wherein in the disabling step is based on at least one condition of the group consisting of a measured power is below a predetermined set point and a measured power indicates a temporal fluctuation in the power used by the rod pump predetermined to indicate a state requiring a shutdown.

9. The method of claim 7 further comprising: (a) measuring a temperature of a polish rod; and (b) disabling the rod pump based on the measured polish-rod temperature.

10. The method of claim 7 further comprising: (a) measuring a tubing pressure; and (b) disabling the rod pump based on the tubing pressure.

11. The method of claim 7 further comprising: (a) determining a rod-pump run time; and (b) changing, using the rod-pump run time and a target run time, at least one of the group consisting of a target rod-pump duty cycle, a target rod-pump period, and a rod-pump off time.

12. The method of claim 11 wherein the changing step includes maintaining the rod-pump target duty cycle and applying at least one modification of the group consisting of decreasing the rod-pump off time if the rod-pump run time is greater than the target run time and increasing the rod-pump off time if the rod-pump run time is less than the target run time.

13. The method of claim 11 wherein the changing step includes maintaining the target rod-pump period and applying at least one modification of the group consisting of decreasing the rod-pump off time if the rod-pump run time is greater than the target run time and increasing the rod-pump off time if the rod-pump run time is less than the target run time.

14. The method of claim 11 wherein the changing step includes one of the group consisting of decreasing the rod-pump off time by a first predetermined percentage if the rod-pump run time is greater than the target run time and increasing the rod-pump off time by a second predetermined percentage if the rod-pump run time is less than the target run time.

15. The method of claim 14 wherein the first predetermined percentage is equal to the second predetermined percentage.

16. The method of claim 13 wherein the changing step is one of the group consisting of decreasing the rod-pump off time by a first amount that depends on a difference between the rod-pump run time and the target run time if the rod-pump run time is greater than the target run time and increasing the rod-pump off time by a second amount that depends on a difference between the rod-pump run time and the target run time if the rod-pump run time is less than the target run time.

17. The method of claim 16 wherein the first amount is equal to the second amount.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description, appended claims, and accompanying drawings where:

(2) FIG. 1 is a schematic view illustrating an exemplary pump-controller for use with electric pumping units according to an aspect of the invention.

(3) FIG. 2 is a schematic view illustrating an exemplary pump-controller for use with gas powered pumping units according to an aspect of the invention.

(4) FIG. 3 is an exemplary flow diagram for a timer mode of operation.

(5) FIG. 4 is an exemplary flow diagram for an automatic mode of operation.

(6) FIG. 5 is an exemplary flow diagram for a pump-control algorithm to adjust the off-time settings for the pump.

(7) FIG. 6 depicts an exemplary current-vs-time profile (AMP wave) for an electric pump.

(8) FIG. 7 depicts an exemplary pressure-vs-time profile for a pump.

(9) FIGS. 8A-8D depict exemplary operational states of a pump.

DETAILED DESCRIPTION

(10) In the summary above, and in the description below, reference is made to particular features of the invention in the context of exemplary embodiments of the invention. The features are described in the context of the exemplary embodiments to facilitate understanding. But the invention is not limited to the exemplary embodiments. And the features are not limited to the embodiments by which they are described. The invention provides a number of inventive features which can be combined in many ways, and the invention can be embodied in a wide variety of contexts. Unless expressly set forth as an essential feature of the invention, a feature of a particular embodiment should not be read into the claims unless expressly recited in a claim.

(11) Except as explicitly defined otherwise, the words and phrases used herein, including terms used in the claims, carry the same meaning they carry to one of ordinary skill in the art as ordinarily used in the art.

(12) Because one of ordinary skill in the art may best understand the structure of the invention by the function of various structural features of the invention, certain structural features may be explained or claimed with reference to the function of a feature. Unless used in the context of describing or claiming a particular inventive function (e.g., a process), reference to the function of a structural feature refers to the capability of the structural feature, not to an instance of use of the invention.

(13) Except for claims that include language introducing a function with means for or step for, the claims are not recited in so-called means-plus-function or step-plus-function format governed by 35 U.S.C. 112(f). Claims that include the means for [function] language but also recite the structure for performing the function are not means-plus-function claims governed by 112(f). Claims that include the step for [function] language but also recite an act for performing the function are not step-plus-function claims governed by 112(f).

(14) Except as otherwise stated herein or as is otherwise clear from context, the inventive methods comprising or consisting of more than one step may be carried out without concern for the order of the steps.

(15) The terms comprising, comprises, including, includes, having, haves, and their grammatical equivalents are used herein to mean that other components or steps are optionally present. For example, an article comprising A, B, and C includes an article having only A, B, and C as well as articles having A, B, C, and other components. And a method comprising the steps A, B, and C includes methods having only the steps A, B, and C as well as methods having the steps A, B, C, and other steps.

(16) Terms of degree, such as substantially, about, and roughly are used herein to denote features that satisfy their technological purpose equivalently to a feature that is exact. For example, a component A is substantially perpendicular to a second component B if A and B are at an angle such as to equivalently satisfy the technological purpose of A being perpendicular to B.

(17) Except as otherwise stated herein, or as is otherwise clear from context, the term or is used herein in its inclusive sense. For example, A or B means A or B, or both A and B.

(18) FIG. 1 shows a control unit 100 for pumping units that have an electric drive motor. Utility power will come into the unit and connect to the input terminals of the contact block 104. An current (AMP) sensor 106 sends current measurements to a controller 102. The control power transformer 108 input is connected to the utility power input terminal providing constant power to the controller regardless of the contact block position. Output power from the transformer 108 powers the controller 102. The contact block 104 is connected to the controller 102. The controller 102 is connected to, and collects information from, a polish-rod temperature probe 120, and tubing-pressure transducer 110. When the controller 102 starts the pump, it sends control power to the contact block energizing an electromagnet, closing the contacts, allowing power to the drive motor. When the motor is running, the controller monitors tubing pressure, polish rod temperature, and current draw. When a pump off condition is indicated in the data from one or more sensors, the pump is turned off.

(19) FIG. 2 shows a control unit 200 for pumping units that have a gas-powered engine used to operate the pump. Power will be supplied to a contact block 204 from a battery (e.g., 12V or 24V). A controller 202 will get power from the input terminals of the contact block 204 providing constant power to the controller 202 regardless of the contact block position. The contact block 204 is connected to the controller 202. The controller 202 is connected to, and collects information from, a fuel-usage sensor 230, a polish-rod temperature probe 220, and a tubing-pressure transducer 210. (In addition to, or instead of, the fuel-usage sensor 230, the controller may monitor an air-usage sensor such as a mass air-flow sensor to monitor the pump's power consumption.) When the controller 202 starts the pump, it sends control power to the contact block 204 energizing an electromagnet, closing the contacts, allowing power to an electric clutch on the pumping unit, starting the pump operation. When the clutch is engaged, the controller 202 monitors tubing pressure, polish rod temp, and fuel/air usage. When a pump off condition is indicated in the data from one or more sensors, the pump is turned off.

(20) FIG. 3 shows an exemplary process flow for a timer mode of operation. Various pressure, temperature, and power-usage data (from sensors/transducers) are used in conjunction with user (or factory) settings to control operation of the pump. The user may establish set points and on/off time operation parameters 302 and start the pump 304. (The user may also proceed with some or all parameters at their default values.) In operation, this exemplary process stops 320, 322, 324 the pump when any of the following three safety conditions is met: (1) the high-line pressure 305 is greater than a set point 306, (2) the low-line pressure 307 is less than the set point 308, and (3) the power usage 309 reaches a belt-slippage-condition set point 310. The exemplary flow will also stop the pump if power usage 315, temperature 313, or pressure 311 indicates a pump-off condition 312. The exemplary flow will also stop the pump if the pump run time reaches the maximum run time set point 314. The user may set a delay before stopping 318 the pump for a pump-off (or other) condition. (The ordering of the condition tests depicted in the flow is not important. They tests may be performed in any order or may overlap in time.) If either the pump-off or the user-defined-run-time condition is met, the pump will automatically restart 342 after the pump has been off for a user-defined (or default) off time 340. The process determines the amount of time the pump has been off 338 and this is compared with the user-defined off time 340 to determine whether to restart the pump 342. If any of the safety-conditions 306, 308, 310 are met, the process may attempt to automatically restart 334 the pump after the off time 328 meets a user-defined (or default) off time 330. In this scenario, the automatic restart 334 may also be conditioned 332 on a maximum number of restarts stopped by a subsequent safety trigger 306, 308, 310. The process will count 328 the number of restarts in this condition and the count will be compared the number allowed 332 to determine whether to automatically restart 334.

(21) FIG. 4 shows an exemplary flow for an automatic mode of operation. This is similar to the timer mode of operation. The primary difference is that the time the pump is kept off after a pump-off condition trigger is automatically adjusted according to a pump-control algorithm. The user may establish set points and on/off time operation parameters 402 and start the pump 404. (The user may also proceed with some or all parameters at their default values.) In operation, this exemplary process stops 420, 422, 424 the pump when any of the following three safety conditions is met: (1) the high-line pressure 405 is greater than a set point 406, (2) the low-line pressure 407 is less than the set point 408, and (3) the power usage 409 reaches a belt-slippage-condition set point 410. The exemplary flow will also stop the pump if power usage 415, temperature 413, or pressure 411 indicates a pump-off condition 412. Optionally, the exemplary flow will also stop the pump if the pump run time reaches the maximum run time set point 414. The user may set a delay before stopping 418 the pump for a pump-off (or other) condition. (The ordering of the condition tests depicted in the flow is not important. They tests may be performed in any order or may overlap in time.) If the pump-off condition is met, the pump will automatically restart 442 after the pump has been off for calculated period of time 440. The process determines the amount of time the pump has been off 438 and this is compared with a calculated off time 444 to determine whether to restart the pump 442. If any of the safety-conditions 406, 408, 410 are met, the process may attempt to automatically restart 434 the pump after the off time 428 meets a user-defined (or default) off time 430. In this scenario, the automatic restart 434 may also be conditioned 432 on a maximum number of restarts stopped by a subsequent safety trigger 406, 408, 410. The process will count 428 the number of restarts in this condition and the count will be compared the number allowed 432 to determine whether to automatically restart 434.

(22) FIG. 5 shows an exemplary flow for a pump-control algorithm 444. The algorithm adjusts the time the pump is left in rest after a pump-off trigger based on the user (or factory) defined set point for the run time (the target run time 507). If the actual run time 443 before reaching a pump-off event is greater than the target time 507, 506, the off time is adjusted downward by some percentage, PD (e.g., 10%) 512, 513. (The actual run time 443 may be determined 504 using the time the pump was started 503 and the time the pump is shut down due to a pump-off condition 505.) If the actual run time 443 before reaching a pump-off event is less than the target run time 507, 508, the off time is adjusted upward by some percentage, PU (e.g., 10%) 514, 515. The downward and upward adjustments are not necessarily equal. Nor are they necessarily constant. For example, the adjustments may be functions of the difference between the actual 443 and target 507 run times. If the actual run time 443 is equal to the target run time 507, then the algorithm-adjusted off time is the same as the previously set off time 516, 517. The off time may be adjusted while keeping the overall target period of the pump constant (any modification to the off time is inversely applied to the target run time), in which case the off-time adjustment will modify the target duty cycle of the pump. (target duty cycle=target run time/target period; target period=target run time+off time). The off time may be adjusted while keeping the target run time constant, in which case the off-time adjustment will modify the target period of the pump.

(23) FIGS. 8A-8B illustrate some exemplary potential operations of the pump-control algorithm. FIG. 8A illustrates an exemplary initial-state on-off timing diagram 800. This initial state (state A) includes an initial target run time 802 (target run.sub.0), an initial off time 804 (off.sub.0), and an initial target period (target period0=target run.sub.0+off.sub.0). As described above, the initial-state off time 804 (off.sub.0) may be modified due to a pump-off event in which the actual run time did not equal the target run time in a number of ways. The modified state 810 illustrated in FIG. 8B includes a target run time 812 (target run.sub.B), a modified off time 814 (off.sub.B), and a target period (target period.sub.B=target run.sub.B+off.sub.B). In this modified state (state B), the target period is the same as the initial state. Thus, the target duty cycle in state B differs from that in state A. The modified state 820 illustrated in FIG. 8C includes a target run time 822 (target run.sub.C), modified off time 824 (off.sub.C), and a target period (target period.sub.C=target run.sub.C+off.sub.C). In this modified state (state C), the target run time is the same as for the initial state. Thus, the target period and target duty cycle in state C both differ from that in state A. The modified state 830 illustrated in FIG. 8D includes a target run time 832 (target run.sub.D), modified off time 834 (off.sub.D), and a target period (target period.sub.D=target run.sub.D+off.sub.D). In this modified state (state D), the target duty cycle is the same as for the initial state. Thus, the target run time and target period in state D differ from that in the initial state.

(24) FIG. 6 illustrates an exemplary current wave 602 (or amp wave; the current-vs-time profile for pump operation, shown in FIG. 6 with a dashed line). In this example, a wave period is monitored by measuring the trough-to-trough time of the wave. (The length of time between similar features on the waveform may sometimes be referred to in the art as a wavelength, though it is a temporal rather than a spatial period.) The evolution of the wave period over time 604 is indicated with a dashed line. Early in time 606 (left in the graph), the wave period 604 is at a level that indicates normal operating conditions. Later in time 608 (right in the graph), the wave period 604 has deviated significantly off the normal level (fallen, in this example), indicating a pump-off condition. By monitoring the temporal response of an electric pump's current draw, it is possible to detect a pump-off condition by detecting a change in the temporal response. Similarly, monitoring the temporal response of a gas-powered pump's fuel or air draw (which also indicates power-consumption over time), it is possible to detect a pump-off condition by detecting a change in the temporal response.

(25) FIG. 7 illustrates the time evolution of a the peak pressure during a pump stroke 702. Early in time 706 (left in the graph) the peak pressure 702 is at a level that indicates normal operating conditions. Later in time 708 (right in the graph), the peak pressure 702 has deviated significantly off the normal level (fallen, in this example), indicating a pump-off condition. By monitoring the temporal response of the peak pressure, it is possible to detect a pump-off condition by detecting a change in the temporal response.

(26) While the foregoing description is directed to the preferred embodiments of the invention, other and further embodiments of the invention will be apparent to those skilled in the art and may be made without departing from the basic scope of the invention. Features described with reference to one embodiment may be combined with other embodiments, even if not explicitly stated above, without departing from the scope of the invention. The scope of the invention is defined by the claims which follow.